1. Technical Field
The invention relates generally to intravascular catheters, particularly catheters having a rotating tip, and being useful in removing thrombus from the lumen of a vessel, such as an artery or vein.
2. Description of the Prior Art
During an atherectomy procedure using a rotating catheter, it is often necessary and desirable to route the catheter through a vessel along a guidewire which has been, in turn, threaded through the center of the catheter and partially through the lumen of the vessel. Further, it is desirable to keep the catheter tube located in the vessel following atherectomy to allow threading of the guidewire into and out of the catheter tube; moreover, it is desirable to leave the catheter tube in place without removing it from the vessel in order to change from an atherectomy catheter to a diagnostic device or balloon catheter. Unfortunately, conventional rotating catheters that do not have a guidewire cannot be used for such exchange because they are solid, therefore, no simple easy means exist for providing the desired exchange function.
One approach of conventional devices is found in U.S. Pat. No. 4,696,667 to Masch, which discloses an intravascular catheter including a flexible guidewire housed within a flexible hollow tubular drive member. The tubular drive member is originally attached to a working head at the distal end of the tube and is driven at the proximal end of the tube by a drive assembly. The drive assembly is composed of a series of gears that engage and rotate the tubular drive member. The tubular drive member is stationary and cannot be removed.
Another example is U.S. Pat. No. 4,747,406 to Nash, which discloses a flexible elongated tubular catheter having a tool which rotates at relatively high speeds, for example, 20,000 rpm, located at the distal end of the catheter. The tool used has a central opening and is rotated by a hollow wire drive shaft.
In other catheters of the "Kensey" type, a central passageway in the drive shaft aligns with the central opening of the cutting tool to accept a conventional guidewire. Thus, although the catheter tube can be threaded along a guidewire during the cutting operation, the drive assembly is not removable.
A specific concern to which intravascular therapy has been directed is acute pulmonary thrombosis, a life-threatening condition that is difficult to diagnose and treat. Acute thrombosis can occur in many areas of the vascular system, causing reduced hemodynamic flow and potential problems for the patient. Although current techniques exist for treating thrombosis, each possess drawbacks rendering them overly time-consuming and risky, with limited effectiveness.
Several drug therapies have been proposed for treatment of thrombus, for example, blood thinners such as Streptokinase, Urokinase and Tissue Plasminogen Activator (TPA), and have been found useful in reducing thrombus in patients. However a disadvantage of this approach is that these drugs are slow-acting agents, which in acute conditions like pulmonary thrombosis means that patients do not live long enough for the drug to work. Although at increased dosages the results are somewhat faster, the incidence of internal bleeding becomes a negative factor.
Surgical removal of thrombus-affected vessels has also been performed, but this procedure is much more invasive than drug therapy. Moreover, certain areas of the body are more hazardous for this procedure, further increasing patient risk.
A balloon technique has been utilized for certain thrombus-laden vessels, for example, in the lower extremities. In the legs, a deflated balloon is passed below the desired treatment area, then inflated and withdrawn, pulling debris up with the balloon. A disadvantage of this technique is the hazard of unremoved thrombus chunks flowing upstream and lodging in the vessel lumen.
A "Kensey" type of recanalization catheter has also been studied for use as an interventional approach to thrombosis, for example, an 8 French catheter has been developed by Drs. Kensey and Nash. Although such devices have been found capable of thrombus ablation, they lack diagnostic capabilities and are difficult to maneuver to the correct location. Further, the exposed tip of the catheter has the potential for causing trauma in tight-fitting locations.
An aspirating, low-speed mechanical catheter for percutaneous thrombectomy has also been proposed, e.g., U.S. Pat. No. 4,700,470, using an internal propeller for pulling thrombus in and an external vacuum source to pull debris out through the catheter. Again, neither diagnostic capability nor maneuverability assistance is provided.
In the past, when physicians have had to operate both a rotating catheter device and a fluid dispenser device as a single unit, it was necessary to operate two separate and independent controllers. In other words, a dedicated motor controller was used to control the speed of rotation of the catheter tip and a separate fluid controller was used to control the amount of fluid dispensed, and the two controllers communicated through a separate interface. The operator of such a dual system must be highly trained in order to properly monitor both systems. Further, since the fluid controller system is a general purpose controller system, it provides certain functions that are unneeded for a rotating tip, fluid ejecting catheter device. Hence, the resulting system is far more complex than actually needed and accordingly, more expensive than required.
Examples of prior art catheter motors and motor controller systems include the system manufactured by Norland Corporation, of Fort Atkinson, Wis. under part number TW1. Examples of prior art fluid control systems include the systems shown in U.S. Pat. No. 4,854,324 in the name of Alan D. Hirschman et al and entitled, "Processor Controlled Angiographic Injector Device"; U.S. Pat. No. 4,812,724 in the name of Alois A. Langer et al and entitled, "Injector Control"; U.S. Pat. No. 4,024,864 in the name of Gomer L. Davies et al and entitled, "Injector With Overspeed Protector"; U.S. Pat. No. 3,701,345 in the name of Marlin S. Heilman et al and entitled, "Angiographic Injector Equipment" and U.S. Pat. No. 3,623,474 in the name of Marlin S. Heilman and entitled, "Angiographic Injection Equipment".
Accordingly, there still remains a need for an interventional instrument that percutaneously enters the body and is capable of selective diagnosis when sufficiently close to an affected area of the vascular system, particularly such a device which is useful in evaluating and treating acute thrombosis.
There is also still a need for a rotating intravascular catheter which has a removable drive system for allowing a catheter to remain in place in the vessel of a lumen so that a drive assembly and the guidewire may be interchangeably routed through the center of the catheter.
There is a also a further need for an improved combination rotational motor and fluid infusion controller for catheters having rotating tips, which can be effectively manipulated by a single operator during an intravascular surgical procedure.